Colombians vote Sunday in a presidential election characterized by a clash of personalities and relentless mudslinging that have overshadowed differences on how to put an end to a half-century of guerrilla violence.

Despite presiding over one of Latin America's fastest-growing economies, support for President Juan Manuel Santos' re-election has been falling steadily for months, especially among poor Colombians who haven't benefited as much from the economic boom.

Amid fatigue with Santos' rule, former finance chief Oscar Ivan Zuluaga has emerged as the strongest challenger thanks to the backing of his one-time boss and mentor, the still-popular but polarizing former President Alvaro Uribe.

The last polls published a week ago placed the two in a dead heat, with about 29 percent support each, below the 50 percent threshold needed to avoid a June runoff. The remaining three candidates trailed by about 20 percentage points.

The two conservative front-runners served simultaneously in Uribe's Cabinet, where they backed a free trade agreement and close anti-narcotics cooperation with the United States.

Where they differ is on how to manage an 18-month peace process with the Revolutionary Armed Forces of Colombia, or FARC, the country's largest rebel army.

Santos has made the prospect of a deal to end the conflict the centerpiece of his campaign. But concerns that rebel leaders, on the ropes after a decade-long US-backed offensive, will get off scot-free for their crimes have been fueling mistrust of the process that Santos' opponents have been quick to seize on.

Although Zuluaga says he too favors a negotiated settlement, he says if elected he'll give FARC negotiators in Cuba a week to demonstrate their commitment to peace by declaring a permanent cease fire.

Zuluaga is also threatening to take a tougher stance on Venezuela, saying in a debate this week that he won't remain "silently complicit" as President Nicolas Maduro jails opponents and stamps out anti-government protests. Santos has been careful not to provoke the socialist president, calculating that extensive commercial ties with the country and relations with leftist governments in South America could suffer.

But those policy differences have largely been engulfed in the past two weeks by a string of bitter attacks and shocking revelations that have left many Colombians ashamed of their politicians after more than a decade of economic and security improvements.

It began with media reports that Santos' campaign manager, J.J. Rendon, received $12 million from the nation's biggest drug traffickers to help negotiate their surrender. Rendon quickly resigned after acknowledging he interceded in the case, though has denied taking any money.

Meanwhile, Zuluaga's campaign has been reeling over the arrest of a computer expert who worked for his campaign and is accused of hacking into the emails of FARC negotiators and even the president.

Zuluaga denounced the arrest as a desperate ploy to derail his campaign. But the emergence of a clandestinely shot video where the candidate listens as the alleged hacker outlines his strategy to undermine the peace talks have cast doubt on his claim that he had no knowledge of the consultant's illegal activities.

The tensions came to a head in a feisty exchange at a televised debate this week where Santos accused his rival of being Uribe's "puppet" and Zuluaga fired back: "You must show me respect."

It's unclear if the last-minute feuding will affect voter preferences.

So far, none of the other candidates — former Bogota Mayor Enrique Penalosa , former Defense Minister Marta Lucia Ramirez and Clara Lopez of the leftist Democratic Pole party — appear to have capitalized on widespread disgust with the two better-funded campaigns.

Regardless of who wins, the polarizing rancor unleashed by the race won't be easy to mend.

"The entire political class comes out looking bad," said Ivan Garzon, a political scientist at the University of the Savannah in Bogota.


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